Facial malformations are among the most common birth defects, and these can impact patients' health and psychological well-being profoundly. However, the underlying mechanisms causing these structural defects are poorly understood. We know that a variety of craniofacial malformations are caused by disruptions to normal signaling by fibroblast growth factors (FGFs) during development. FGF signaling controls the activity of cells in the developing face, but how FGF signaling does this is largely unknown. To better understand the mechanisms by which FGF signaling controls craniofacial development, preliminary studies have identified a gene, CRISPLD2, whose expression is affected by FGF signaling and whose disruption is associated with cleft lip/palate malformations. It has been further shown that expression of this gene affects cell motility, that it is expressed in the tissus of the face during early facial patterning, and that altered gene expression levels cause altered facial shapes in chick and zebrafish embryos. Therefore, this project tests the hypothesis that, as a downstream effector of FGF signaling during facial morphogenesis, CRISPLD2 affects cell behaviors, including proliferation, migration, and/or polarization of the facial mesenchyme and/or ectoderm, which in developing tissues together determine the gross morphology of the face. A focused, two-year investigation is proposed to investigate the cellular and morphological effects of CRISPLD2, utilizing the chick model system for rapid results. For the first Aim, the effects of altered CRISPLD2 expression on neural crest cell behaviors in vitro will be examined. For the second Aim, the effects of altered CRISPLD2 expression in chick embryos will be evaluated by quantifying cell behaviors and correlating them to craniofacial shape in the same specimens. This approach will link gene expression levels of CRISPLD2 with cellular activity and the generation of craniofacial shape. The results of this work will provide important insights into how FGF signaling controls facial development and will identify specific mechanisms causing cleft lip/palate and other types of structural malformations of the face.